1. Field of the Invention
The present invention relates to pipe anchor construction. More particularly the invention relates to intermittently anchored high temperature underground conduit systems which employ insulating flange assemblies for accomplishing the metal-nonmetal conduit connections.
Because these underground conduit systems are subject to variations in temperature, they are also subject to expansion and contraction. Accordingly, it is necessary to provide intermittent expansion joints along the length of conduit. To insure proper allocation of the conduit expansion and contraction, it is necessary to anchor the conduit against longitudinal movement at locations between the expansion joints.
2. Description of the Prior Art
For the most part the prior art has used metallic outer conduit casings such as that described in U.S. Pat. No. 3,168,114 which issued Feb. 2, 1965 to J. L. Martin. The outer metal casing was chosen primarily because of the ability to withstand high temperatures. However, the choice of metallic casings is unattractive from the standpoint of expense, susceptibility to corrosion, and its propensity to expand and contract.
More recently, however, the prior art has gone to non-metallic outer casings for high temperature fluid conduits. This is represented by an anchored high temperature fluid conduit system manufactured by RIC-WIL, Incorporated of Brecksville, Ohio which employs an outer casing of fiberglass reinforced plastic conduit. This is identified in RIC-WIL Drawing No. SKA 4169 E.
In the RIC-WIL reference, however, the non-metallic outer casing is directly bonded to an annularly disposed steel casing at all nonmetallic-metallic connection locations by means of an epoxy resin bond. This type of connection suffers from the disadvantages of high temperature breakdown, consequential leaking, and affords a more limited access to the central high temperature conduit.
It has become conventional in the prior art as represented by the Martin pipe anchor and by U.S. Pat. No. RE 22,988 issued Mar. 16, 1948 to W. S. McLeish to employ metallic anchor plates depending from the central high temperature conduit, extending through the outer casing, and embedded in a surrounding concrete block.
These anchor plates, while providing a rigid anchor means for the conduit system also conduct heat from the high temperature conduit to the outer casing, thereby making the use of a non-metallic outer casing impracticable when using the insulating means and connectors of the prior art.